In chemical processes where solid material is produced or used, solids may adhere to the interior walls of and any internals in the vessels wherein the chemical processes take place. Such adhesion can be so strong that after emptying the vessel, the solid material remains adhered to the interior walls as so-called fouling. Especially in batch or semi-batch processes, it is desired that before a next batch is performed all of the fouling is removed. Because new fouling material may adhere relatively fast to fouling that is already present (i.e. from a previous batch).
It is known to remove fouling by using cleaning agents, such as acetone. However, it was found that a fraction of a fouling may not be soluble in acetone so that a thin fouling layer stays behind to which new fouling material may adhere relatively fast. Especially, it has appeared that with acetone not all fouling can be removed in a case where the fouling is produced in a process for making polymer polyols, which are dispersions of solid polymer in a liquid polyol.
The object of the present invention is to find a cleaning agent which effectively removes the fouling produced in chemical processes as described above.
Surprisingly, it was found that an aqueous solution of a guanidine is such effective fouling removing agent.